This invention relates to a storage apparatus. More particularly, this invention relates to an apparatus with automatic insertion and retrieval of samples from a storage container. More specifically, this invention relates to an apparatus for the preservation of biological specimens at various temperatures, including but not limited to the temperature of liquid nitrogen.
When properly treated, biological specimens can be stored almost indefinitely at temperatures approaching that of liquid nitrogen so long as that temperature is maintained. However, once the temperature of a specimen is raised, especially to a level where thawing occurs, the integrity of the specimen suffers if the specimen is then refrozen.
Many conventional cryogenic storage units are simple containers with removable racks having multiple shelves. Specimens are inserted and removed from the storage units manually through a door in the top of the unit. Retrieval operations always necessitate the removal of many specimens in the same rack as the desired specimen.
Such conventional cryopgenic storage units are inadequate for several reasons. Firstly, the storage temperature is not uniform and depends on the vertical location within the storage unit. Thus, some specimens may not be subjected to sufficiently low temperatures during storage. Secondly, the insertion and retrieval of specimens exposes many, if not all, of the stored specimens to ambient thawing temperatures, with a resultant decrease in the viability of the refrozen cells. Thirdly, ice crystals form on the specimens because of repeated exposure to the atmosphere during insertion and retrieval operations. This ice build up inhibits the reading of identification tags affixed to the specimens. In addition, the storage units are limited in their storage capacity because the units are generally no higher than the waist to facilitate manual insertion and retrieval operations.
U.S. Pat. No. 4,969,336 to Knippscheer et al. discloses a cryogenic storage device which corrects the abovementioned disadvantages of conventional cryogenic storage units. The device includes a pair of endless belts which move a multiplicity of specimen-containing vials along a snaking path. The locations of the vials within the unit are tracked by a computer which controls insertion and retrieval operations.
The cryogenic storage unit of U.S. Pat. No. 4,969,336, although superior to conventional cryogenic storage units which are manually operated, is subject to the disadvantage of having many moving parts. Such moving parts suffer from wear and thus require substantial repair and maintenance efforts.